Abstract BACKGROUND: Long-term follow-up of population-based randomized, controlled trials (RCTs) have demonstrated that screening for abdominal aortic aneurysms (AAAs) measuring 3 cm or greater decreases AAA-related mortality rates in men aged 65 years or older. PURPOSE: To systematically review evidence about the benefits and harms of ultrasonography screening for AAAs in asymptomatic primary care patients. DATA SOURCES: MEDLINE, the Database of Abstracts of Reviews of Effects, the Cochrane Central Registry of Controlled Trials (January 2004 through January 2013), clinical trial registries, reference lists, experts, and a targeted bridge search for population-based screening RCTs through September 2013. STUDY SELECTION: English-language, population-based fair- to good-quality RCTs and large cohort studies for AAA screening benefits as well as RCTs and cohort and registry studies for harms in adults with AAA. DATA EXTRACTION: Dual quality assessment and abstraction of study details and results. DATA SYNTHESIS: Reviews of 4 RCTs involving 137Â 214 participants demonstrated that 1-time invitation for AAA screening in men aged 65 years or older reduced AAA rupture and AAA-related mortality rates for up to 10 and 15 years, respectively, but had no statistically significant effect on all-cause mortality rates up to 15 years. Screening was associated with more overall and elective surgeries but fewer emergency operations and lower 30-day operative mortality rates at up to 10- to 15-year follow-up. One RCT involving 9342 women showed that screening had no benefit on AAA-related or all-cause mortality rates. LIMITATIONS: Trials included mostly white men outside of the United States. Information for subgroups and about rescreening was limited. CONCLUSION: One-time invitation for AAA screening in men aged 65 years or older was associated with decreased AAA rupture and AAA-related mortality rates but had little or no effect on all-cause mortality rates. PRIMARY FUNDING SOURCE: Agency for Healthcare Research and Quality.